All are true about paralytic squint except:
**Core Concept**
Paralytic squint, also known as paralytic strabismus, is a type of strabismus caused by weakness or paralysis of one or more extraocular muscles, leading to misalignment of the eyes. This condition can result from various causes, including cranial nerve palsies, muscle trauma, or neurodegenerative diseases.
**Why the Correct Answer is Right**
Paralytic squint is characterized by a lack of coordination between the extraocular muscles, leading to impaired eye movement and alignment. The affected muscle may be weak or paralyzed, causing the eye to deviate in a specific direction. In some cases, the deviation may be constant, while in others, it may be intermittent. The underlying cause of paralytic squint can be determined by examining the cranial nerves responsible for controlling the extraocular muscles.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because paralytic squint is not caused by a refractive error, but rather by a weakness or paralysis of the extraocular muscles.
**Option B:** This option is incorrect because while convergence is an important aspect of eye movement, paralytic squint is not primarily a disorder of convergence.
**Option C:** This option is incorrect because paralytic squint is not a type of nystagmus, which is a different condition characterized by involuntary, rhythmic eye movements.
**Clinical Pearl / High-Yield Fact**
In paralytic squint, the key to diagnosis is identifying the underlying cause of muscle weakness or paralysis, which can often be determined by examining the cranial nerves responsible for controlling the extraocular muscles. This requires a thorough understanding of the anatomy and physiology of eye movement.
**Correct Answer:** A.